Spectral re-growth due to an amplifier's non-linear distortion characteristics has become an important issue in modern amplifier design. With the increased demand for channel allocations, closer channel spacing and new modulation techniques with their higher peak to average power ratios comes an increased demand for amplifiers exhibiting extremely high linearity. Class A amplifiers exhibit good linearity but they suffer from poor efficiency and high cost when high power levels are required. Class A/B amplifiers are more cost effective but suffer from poor linearity. Methods of correction exist which can improve an amplifier's linearity. Pre-correction with linearizers will improve an amplifier's linearity, but since such linearizers are open-loop they exhibit stability problems with time and temperature. Feedforward correction of an amplifier will improve the amplifier's linearity, but this type of correction requires a higher power amplifier due to losses inherent with the feedforward correction. Feedback correction will improve an amplifier's linearity, but these are usually band width limited.
A feedforward system in the prior art of interest takes the form of the U.S. Pat. No. to D. Danielsons 5,850,162. In that system, an output amplifier having a non-linear signal response characteristic is linearized by selecting a preceding amplifier in a multi-stage amplifier network and providing feedforward overcorrection to the preceding amplifier to compensate for the non-linear signal response characteristics of the output amplifier.
It is contemplated that an amplifier having non-linear response characteristic can be linearized with a corrected input signal obtained from another amplifier which has been selected as exhibiting similar non-linear characteristics as the amplifier to be corrected. Also, it is contemplated that practicing the invention will result in efficiencies rivaling that of a Class A/B amplifier while yielding linearity that exceeds that of a Class A amplifier with wide bandwidth operation.
It is further contemplated that the invention herein may reduce the memory-full and/or non-memory-full distortions of an amplifier having a non-linear signal characteristic. Memory-full distortions refer to time dependent or historic distortions whereas non-memory-full distortions refer to non-time dependent distortions.